1. Field of the Invention
The present invention relates to an optical interconnection apparatus installed into systems such as a computer such as a server, a client, etc. and a router, etc. to serve as an interface between an LSI such as CPU, a memory, etc. and an opto-electric hybrid substrate, and an interconnection module constituting the optical interconnection apparatus.
2. Description of the Prior Art
With the progress of the telecommunication technology and the information processing technology, the density of the electric wirings for connecting the electronic circuits in various systems such as the computer, the large-capacity switching system, etc. is increased higher. Such higher density acts as the main cause of an obstruction to larger scale and higher performance of the system. Also, the conspicuous progress of LSI in recent years brings about the higher density of input/output terminals of LSI and the higher density of the electric wirings provided in LSI, which act as the bottlenecks in performance improvement. In order to overcome such problems, the optical interconnection technology for optically connecting the electronic circuits mutually is watched with interest.
Normally, the optical interconnection apparatus is constructed by arranging two-dimensionally parts, that are the light emitting element such as the surface emitting semiconductor laser (VCSEL: Vertical Cavity Surface Emitting Laser) or the like, the driver IC for driving the light emitting element, the light receiving element such as the photodiode or the like, the receiver IC for driving the light receiving element, and the like (referred to as “interconnection modules” hereinafter), on the submounting substrate. In many cases, the LSI, in which a CPU circuit, a memory circuit, etc. are formed, as well as these interconnection modules is mounted on the submounting substrate.
However, the optical interconnection apparatus in the prior art has such a drawback that, since respective interconnection modules are arranged two-dimensionally, a packaging area become large and thus reduction in size is difficult. Also, there is such a problem that, since lengths of the electric wirings for connecting respective interconnection modules become longer, a high-speed operation is impeded and also an S/N ratio is deteriorated due to the crosstalk noise.
Also, the optical interconnection apparatus in which the silicon substrate is used as the submounting substrate, then the driver circuit, the receiver circuit, the CPU circuit, etc. are formed on the silicon substrate, and then the light emitting element and the light receiving element are mounted onto the silicon substrate has been developed. However, in the optical interconnection apparatus of this type, since the driver circuit, the receiver circuit, the CPU circuit, etc. are monolithically integrated, it is difficult to change the circuit and thus the versatility is low.
In order to miniaturize the optical interconnection apparatus, it may be considered that respective interconnection modules are arranged three-dimensionally (3D). For example, the optical element (the light emitting element or the light receiving element) is mounted under the submounting substrate and also the driver IC or the receiver IC is mounted on the submounting substrate. However, if the interconnection modules are arranged three-dimensionally, it is impossible to connect electrically respective interconnection modules.
Also, for example, the surface emitting semiconductor laser has electrodes on a surface on the light emitting side and a surface on the opposite side respectively. Therefore, the electrode provided to one surface side can be connected directly to the submounting substrate, but the electrode provided to the other surface side must be connected to the submounting substrate by the method such as the wire bonding, or the like. As a result, there is such a problem that the packaging step becomes complicated.
In addition, the optical interconnection apparatus in the prior art has such another drawback that, since the relatively expensive substrate such as the ceramic substrate, the silicon PLC (Planar Lightwave Circuit) substrate, or the like is used as the submounting substrate, a production cost is increased.